| Ginseng is a cherish Chinese medicinal herb with a variety of effects,and the Ministry of Health of China has classified ginseng as a new resource food in 2012,with an increasing market demand in recent years.However,ginseng is often infested with pests and diseases during cultivation,and abuse of pesticides causes a large number of pesticide residues,which brings great obstacles to the production and sales of ginseng,and also brings harm to people's health.The compound preparation of pyraclostrobin and fluxapyroxad can effectively expand the control spectrum of pathogens,delay crop aging,increase crop stress resistance and improve crop quality.The potential application of the compound fungicide in ginseng cultivation has attracted the attention of the majority of scientific researchers and farmers.In this study,we established a residue analysis method of pyraclostrobin and fluxapyroxad on ginseng,analyzed the residual digestion of pyraclostrobin and fluxapyroxad in ginseng plants and soil,analyzed the final residues of pyraclostrobin and fluxapyroxad in ginseng plants,fresh ginseng,dry ginseng and soil,and evaluated the dietary risks of pyraclostrobin and fluxapyroxad on ginseng,providing a theoretical basis for the safe use of pyraclostrobin and fluxapyroxad on ginseng.1.High performance liquid chromatography-tandem mass spectrometry?HPLC-MS/MS?method was established for the determination of pyraclostrobin and fluxapyroxad in the ginseng plant,fresh ginseng,dry ginseng and ginseng soil.Mass spectrometry conditions and mobile phase were optimized.At the same time the extraction condition and purification condition were optimized.The samples were extracted with a mixture of acetonitrile and water,ginseng plants were purified by PSA,C18 and GCB.Fresh ginseng,dry ginseng and soil were purified by PSA and C18.Detection of analytes was performed by HPLC-MS/MS.The average fortified recoveries of pyraclostrobin and fluxapyroxad in four sample matrixes?ginseng plants,fresh ginseng,dry ginseng and soil?were respectively between 76.7%-105.3%and 75.0%-98.6%with the relative standard deviations of 0.8%-4.6%and 0.8%-6.6%.The recoveries and relative standard deviation of pyraclostrobin and fluxapyroxad are at the range of allowable in pesticide residue analysis.2.The residual digestion of pyraclostrobin and fluxapyroxad on ginseng plants and soil was measured.The results showed that the dissipation of pyraclostrobin and fluxapyroxad is accord with first-order kinetics equation.The half-life of pyraclostrobin in ginseng plants and soil were0.18-8.39 d and 4.11-13.17 d,respectively.The half-life of fluxapyroxad in ginseng plants and soil were 6.78-21.78 d and 3.73-15.39 d,respectively.The half-life of the two pesticides,t1/2,is less than 30 d.3.The final residues of pyraclostrobin and fluxapyroxad on ginseng plants,fresh ginseng,dry ginseng and soil were measured.In 2017,the final residue test was done in Jian and Fusong of Jilin province.The 42.4%pyraclostrobin·fluxapyroxad suspending agent spraying at a dose of 190.8 g a.i./ha and 286.2 g a.i./ha.The spraying was two times and three times.The last spraying were 21 d and 28 d before harvest intervals,the final residues of pyraclostrobin and fluxapyroxad in ginseng plant were 1.734-52.133 mg/kg and 3.617-134.116 mg/kg,respectively.The residues in fresh ginseng were less than 0.01 mg/kg-0.139 mg/kg and less than 0.01mg/kg-0.248 mg/kg,respectively.The residues in dry ginseng were less than 0.01 mg/kg-0.203mg/kg and 0.011-0.535 mg/kg,respectively.The residues in soil were 0.020-0.248 mg/kg and0.014-0.306 mg/kg,respectively.In 2018,the final residue test was done in yanji and huanren.The 42.4%pyraclostrobin·fluxapyroxad suspending agent spraying at a dose of 190.8 g a.i./ha.The spraying was two times.The last spraying were 21 d and 28 d before harvest intervals,the final residues of pyraclostrobin and fluxapyroxad in ginseng plant were 29.189-60.668 mg/kg and52.746-151.614 mg/kg,respectively.The residues in fresh ginseng were less than 0.01 mg/kg and less than 0.01 mg/kg-0.011 mg/kg,respectively.The residues in dry ginseng were less than0.01 mg/kg.The residues in soil were 0.014-0.217 mg/kg and 0.010-0.049 mg/kg,respectively.4.Assessed the dietary risk of pyraclostrobin and fluxapyroxad in ginseng based on experimental data,the results showed that the acute dietary risks of pyraclostrobin in fresh ginseng and dry ginseng were 0.251×10-1%-0.406×10-1%and 0.149×10-1%-0.198×10-1%,chronic dietary risk were 57.98%.The acute dietary risk of fluxapyroxad in fresh and dry ginseng were 0.087×10-1%-0.119×10-1%and 0.067×10-1%-0.086×10-1%,The chronic dietary risks were 92.80%-92.81%and 92.79%-92.80%;which is less than 100%,indicating that the resulting risk was acceptable. |
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